Late to the party as usual, I just went to see this at the weekend and enjoyed it a lot.

Regarding the discussion on the shot of Cobb and Mal (really? not Moll?) being old, yet young at the train: I took it that limbo is a much more malleable place than a dream; sure they grew old together over the length of time they subjectively spent in there, but when Cobb sucessfully convinced Mal (honestly?) they had to leave, the physical changes imparted on them by limbo just fell away. Presumably the same would have happenned to Cobb and Saito, we just didn't see it.

Can anyone explain, though, how Arthur destroying the elevator cable (and e-brake) caused the lift to fall in a world with zero-gravity? I didn't quite understand what was going on there.